Threaded fasteners are frequently used in loose and interference fit applications in which it is difficult to work from both sides of workpieces to be secured together. In such applications, it has been the practice to use a fastener installation tool having a key which is inserted into a broached recess of a fastener to hold the fastener stationary while a non-circular threaded nut is threaded on the fastener with the installation tool. When the nut is threaded on the fastener with the tool and the fastener is restrained against rotation by the key to secure the workpieces together in a fastened joint, the fastener is set.
In the prior art, springs were used to prevent the key from rotating relative to the fastener during installation of the nut. Oftentimes, the spring would fatigue and fail during the installation process which requires replacement of the spring in a time consuming process. Because the spring fatigues, the spring was typically manufactured from large diameter spring stock which makes it difficult for an operator of the installation tool to keep the key engaged in the recess of the fastener during the installation process. Without proper engagement of the key with the recess of the fastener, the nut will not thread on the fastener in a reliable manner. Unreliable installations are not acceptable in mission critical applications. Also, a problem that exists with this type of fastener installation tool is the tendency of the key to twist or otherwise deform. Additionally, changing the key after damage or to a different sized key is a relatively slow procedure when a spring made from a large diameter spring stock is used to prevent the key from rotating relative to the fastener during installation of the nut.